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Practical Devices XM5 - Page 3

post #31 of 397
12/15/08 at 12:34am
I'm getting more and more excited about this thing, wish Larry was feeling better so he could get on his review....
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post #32 of 397
12/15/08 at 12:45am
I just ordered an XM5 with BUF634. I'm anxious to test it against my Pico DAC. I don't plan to use the DAC much now but it's always a good thing to have...it will serve as my iPod amp for HD650 mainly, also ER4P & 325i...should have more than enough power.

I can't wait!

I look forward to reading Larry's review also.
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post #33 of 397
12/15/08 at 2:24am
Quote:
Originally Posted by GreatDane View Post
I just ordered an XM5 with BUF634.
Same thing I have. It's a solid unit with some handy features I think. Thinking about getting the HD650s myself in the next couple days.

I've been using it mainly connected to my computer as a DAC+AMP though, haven't used it as a portable much yet.
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post #34 of 397
12/15/08 at 2:34pm
Quote:
Originally Posted by GreatDane View Post
I just ordered an XM5 with BUF634. I'm anxious to test it against my Pico DAC. I don't plan to use the DAC much now but it's always a good thing to have...it will serve as my iPod amp for HD650 mainly, also ER4P & 325i...should have more than enough power.

I can't wait!

I look forward to reading Larry's review also.
I'll be interested in reading your results. Mine came with the AD 8397 chip, and it drove my AKG K-240's very well. Supposed to have a bit more output then the OPA 134 with BUF 634.

PD also sent me the OPA134 chips, and I recently installed them as my first chip rolling experiment. The output was less, but still drove the K-240's very well. The sound was slightly different, but I'd have to compare them together to determine which I liked better
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post #35 of 397
12/15/08 at 3:38pm
Quote:
Originally Posted by Harvey/ Ga View Post
I'll be interested in reading your results. Mine came with the AD 8397 chip, and it drove my AKG K-240's very well. Supposed to have a bit more output then the OPA 134 with BUF 634.

PD also sent me the OPA134 chips, and I recently installed them as my first chip rolling experiment. The output was less, but still drove the K-240's very well. The sound was slightly different, but I'd have to compare them together to determine which I liked better
But with the AD8397 you lose the dual mono feature of the amp.
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post #36 of 397
12/15/08 at 3:48pm
What exactly does that mean (the dual-mono stuff)? Yay for n00bs not being afraid to admit it!
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post #37 of 397
12/15/08 at 4:06pm
Quote:
Originally Posted by HeadphoneAddict View Post
But with the AD8397 you lose the dual mono feature of the amp.
True... I'm not that well versed in the significance of that or other 'phone amp features like Xin's 4 channel amps.... we only have 2 ears ???

I'm quite a newbie at this. I do know that i prefer the XM-5 over my Microshar 107B. Perhaps it's fortunate that I can't listen to many of the units that are written about on Head-Fi (altho I'd love to ) I hope to try a few different Op-amps later on to see if there's a difference.
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post #38 of 397
12/15/08 at 4:29pm
In a dual mono configuration, current draw on one channel does not rob the other channel of power. It's like using dual mono block amps in a home speaker rig, where the two channels are isolated from one another. This made a big difference on my Woo WA6 tube amp when the left and right driver tubes were isolated from each other's power supply. It can also assist in better channel separation and soundstage.
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post #39 of 397
12/15/08 at 8:23pm
I will also admit to not know much about the different amp chips, I've never spent the time to experiment even though I've owned a Xin amp in the past that would have allowed me to do so.

Thanks Larry for that explanation about dual mono. I was never quite sure about the advantages.

James tells me that my XM5 has shipped! YEA!
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post #40 of 397
12/15/08 at 8:38pm
I'll throw in another question from the peanut gallery (i.e. me) - what's the impact of using these BUF634 chips? Does it improve SQ? Or does it just let you drive higher impedance headphones?
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post #41 of 397
12/16/08 at 4:23am
They increase current, not voltage. Watts = Volts x Amps and with more current that means more watts (power) at the headphone jack. Comparing to plumbing, the voltage is equivalent to the water pressure, the current is equivalent to the flow rate, and the resistance is like the pipe size.

Of course there are other issues, like how higher headphone impedance (resistance) lowers the current that will flow, and thus power will be different with low impedance vs high impedance headphones. Current is = Voltage/Impedance, so with high impedance headphones you can increase voltage to get more current. Some amps use voltage multipliers internally, especially those that run on 1 or two AA or AAA batteries. I don't think the XM5 does that since it is already 9v.

The thing is, with some amps and low impedance headphones like Grado or Denon they run out of juice, and the buf634 should prevent that from happening. I don't know that it affects driving HD600 as much.

Hopefully an expert will pop in to clarifiy that.
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post #42 of 397
12/17/08 at 11:05pm
Would IEMs like TF10s run out of juice and benefit with BUF634s? Any idea if the buffer chips impact SQ?

Thanks!
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post #43 of 397
12/18/08 at 1:07am
Quote:
Originally Posted by oogabooga View Post
Would IEMs like TF10s run out of juice and benefit with BUF634s? Any idea if the buffer chips impact SQ?

Thanks!
Many IEM like Triple.fi are so efficient they don't run out of juice when you only need 20-30ma to get quite loud, while the D2000 can take about all the power you can throw at it (1800ma) they don't need that much either.
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post #44 of 397
12/18/08 at 1:08pm
Quote:
Originally Posted by HeadphoneAddict View Post
They increase current, not voltage. Watts = Volts x Amps and with more current that means more watts (power) at the headphone jack. Comparing to plumbing, the voltage is equivalent to the water pressure, the current is equivalent to the flow rate, and the resistance is like the pipe size.

Of course there are other issues, like how higher headphone impedance (resistance) lowers the current that will flow, and thus power will be different with low impedance vs high impedance headphones. Current is = Voltage/Impedance, so with high impedance headphones you can increase voltage to get more current. Some amps use voltage multipliers internally, especially those that run on 1 or two AA or AAA batteries. I don't think the XM5 does that since it is already 9v.

The thing is, with some amps and low impedance headphones like Grado or Denon they run out of juice, and the buf634 should prevent that from happening. I don't know that it affects driving HD600 as much.

Hopefully an expert will pop in to clarifiy that.

The XM5 seems interesting I tend to like things with lots fo feautes and customizations.

If i got it I would be using it with a zune 30 and Atrio M5 version 2's.

This talk of opamp rolling and buffer chips is completely foreign to me.

Seeing as my IEM's are not weird or hard to drive do I need to worry about any additional chips or upgrade if I bought this amp?

Is there any real SQ benefit for easy to drive normal IEM's like the Atrio's?
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post #45 of 397
12/18/08 at 10:05pm
Quote:
Originally Posted by swanlee View Post
The XM5 seems interesting I tend to like things with lots fo feautes and customizations.

If i got it I would be using it with a zune 30 and Atrio M5 version 2's.

This talk of opamp rolling and buffer chips is completely foreign to me.

Seeing as my IEM's are not weird or hard to drive do I need to worry about any additional chips or upgrade if I bought this amp?

Is there any real SQ benefit for easy to drive normal IEM's like the Atrio's?
If you have a line out on your DAP that has better sound quality than the headphone jack, then the amp can be a benefit, otherwise with easy to drive IEM using an amp via the headphone out is a waste of time.
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